Two stroke cycle crankcase scavenged internal combustion engine



May 11, 1965 w. TENNEY 3,182,643

TWO STROKE CYCLE CRANKCASE SCAVENGED INTERNAL COMBUSTION ENGINE FiledApril 9, less 4 Sheets-Sheet 1 FIG. 1

INVENTOR. Mum/w A. Tan/mar Irma-vars May 11, 1965 w. L. TENNEY 3,182,643

. TWO STROKE CYCLE CRANKCASE SCAVENGED INTERNAL COMBUSTION ENGINEINVENTOR. I Mann 1. fimvey firrokmm May 11, 1965 w. L. TENNEY 3,182,643TWO STROKE CYCLE CRANKCASE SCAVENGED INTERNAL COMBUSTION ENGINE FiledApril 9, 1963 4 Sheets-Sheet s FIG. E

INVENTOR Alla/AM 1.. firm/7 Arnzuey;

y 1965 w. L. TENNEY 3,182,643

TWO STROKE CYCLE CRANKCASE SCAVENGED INTERNAL COMBUSTION ENGINE FiledApril 9, 1963 4 Sheets-Sheet 4 FILE.

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United States Patent 3,182,643 TWO STROKE CYCLE CRANKCAS'E SCAVENGEDINTERNAL COMBUSTION ENGINE William L. Tenney, Crystal Bay, Minn. FiledApr. 9, 1963, Ser. No. 271,727 11 Claims. (Cl. 123-51) This inventionrelates to two stroke cycle crankcase scavenged internal combustionengines of improved design. engine.

It is known that four-cycle engines may be made to develop peak horsepower at a piston speed of about 4000 feet per minute, and materials andmechanical designs are available which permit operation at such speeds.By contrast, the usual loop-scavenged two-cycle engines develop peakhorse power at piston speeds of about 2000 feet per minute. Heretoforethere has been no design available in the art of two-cycle enginespermitting the peak horse power to be attained at piston speeds in the4000 feet per minute range.

I have discovered certain improvements in the field of two-cycleengines, whereby such engines will develop peak horse power at pistonspeeds of 4000 feet per minute or thereabouts, and it is therefore anobject of the invention to provide such improved two-cycle crankcasescavenged internal combustion engines capable of developing maximumhorse power at or about 4000 feet per minute piston speed.

Here-tofore the fuel mixture scavengedtwo-cycle loopscavenged internalcombustion engines utilizing known design techniques, have yielded aspecific fuel consumption of approximately twice as greatas comparablefour-cycle engines. Consequently the use of large horse power fuelmixture scavenged two-cycle loop-scavenged engines has been restricteddue to their very large tuel; requirement. By contrast the four-cycleengines have had a much better (lower) specific fuel consumption, buteven though capable of operating at higher piston speeds, such enginesare generally heavier and bulkier than two-cycle engines of the samehorse power.

It is an object of the present invention to provide an improvedtwo-cycle cranckcase scavenged internal combustion engine having aspecific fuel consumption comparable with that of founcycle engines ofequal displacement, while at the same time having horse power output fora given cylinder size far greater than that of either the four-cycleover-head valve engines or of the two-cycle loop-scavenged engine.

In two-cycle crankcase scavenged internal combustion engines the ratioof the air pumped from the crankcase to the total volume of the cylinderis known as the delivery ratio (sometimes also called the scavengingratio). It is an object of thepresent invention to provide a reduceddelivery ratio, so that the engine works further down on the curve ofdelivery ratio, with resultant improved fresh charge trapping efiiciencyand specific fuel consumption.

According the Hans List as reported in scavenging of Two Stroke CycleDiesel Engines by Svveitzer, page 45 in a uniflow scavenged engine thefresh charge trapping efficiency can be virtually 100% up to ascavenging ratio of approximately 60% 70%. It is an object of thepresent invention to provide a two-stroke cycle, crankcase scavengedinternal combustion engine wherein a uniflow scavenging pattern isprovided and which operates at or near the 60%70% ratio atfull throttle,with resultant reduction in the full throttle specific fuel consumptionto approximately half thatof prior loop-scavenged two-cycle engines andwith specific consumption approximately equal to that of four-cycleengines of equivalent cylinder size.

It is an object of the invention to provide such "ice In loop-scavengedtwo-cycle engines all the ports are arranged around the cylinder atsubstantially the same level, so as to be uncovered by'the piston as itproceeds towards its lowermost position, the ports on one side of thecylinder generally being devoted to induction and on the other sidebeing generally devoted to exhaust of the burned gases. The height ofthe ports as a percentage of piston travel is limited. Accordingly, insuch loopscavenged engines, there is in effect an insufiiciency ofpiston-stroked cylinder wall area that can bedevoted to porting thecylinder. The net efiect, has been that even though higher piston speedscan be mechanically very high, and the power delivery curve may be madecor respondingly flatter and fatter, without reliance much uponpulsations (resonance) in exhaust components for increasing thehorsepower at certain speeds.

It is another object of the invention to provide an improved two-cycleengine wherein the exhaust valving is accomplished by separate pistonsreciprocating generally in opposite phase to the main piston with theancillary result that such engines may be dynamically balancedadvantageously by properly weighing such separate pistons in respect tothe main piston.

It is an "object of the invention to provide improved mechanical designsutilizable in internal combustion engines of the carburetor offuelinjection spark ignition type and diesel 'types utilizing self ignitionor spark ignition.

Otherand further objects are those inherent in the invention hereinillustrated, described and claimed and will be apparent as thedescription proceeds.

To the accomplishment of the foregoing and related ends, this inventionthen comprises the features hereinafter fully described and particularlypointed out in the claims, the following description setting forth indetail certain illustrative embodiments of the invention, these beingindicative, however, of but a few of the various ways in which theprinciples of the invention may be employed.

The invention is illustrated with reference to the drawings wherein:

FIGURE 1 is a transverse sectional view of one form of engine embodyingthe present invention;

FIGURE 2 is a transverse sectional view through a modified form ofengine embodying the present invention; p 1

FIGURE 3 is a transverse sectional view through another modified form ofengine embodying the persent invention; V l i a FIGURE 4 is asideelevational view taken in the direction of arrows 4-4 of. FIGURE 3; 7

FIGURE 5 is a transverse sectional view taken along the lines and in thedirection of arrows 5-5 of FIG, URE 3;

FIGURE 6 is aside elevational view similar to FIG- URE 4 showing: aslightly modified form of engine embodying the invention; and

FIGURE 7 is a transverse sectional view taken in the direction of arrows7-7 of FIGURE 6. r

Throughout the drawings corresponding numerals refer to the same parts.i

Referring to FIGURE 1 there is illustrated an internal combustion engineembodying the present invention. This engine utilizes a main crankcasegenerally designated and cylinder generally designated 11, attachedthereto. The crankcase 10 is split as, for example, at the flanges 12 sothat it may be opened. Any style of crankcase construction may be used.

The cylinder generally designated 11 begins at the lower edge 11A andhas a main cylinder portion beginning at 11A and continuing to junction4444. The cylinder 11 thence continues upwardly through a supplemental(or exhaust) cylinder portion 11D to upper termination 11E. In the formof engine shown in FIG- URE 1, the cylinder is of the same diameterthroughout the full length of portions 11C and 11D.

Part way up the cylinder from the bottom there are provided a pluralityof induction ports 14 which are spaced around the cylinder. Thedimensions of these ports, the number and size of lands between them,and direction of induction through such ports may be varied according togood design practice. These ports 14 form the upper termination of atransfer passage 15 which entirely encircles the cylinder 11 at and tosome extent below the ports, it being noted that portion 11C of thecylinder forms the inner wall of the transfer passage 15 whereas theouter wall of such passage is formed by the shell 16. The shell curvesinwardly at 16A and joins the cylinder wall at 16B. The transfer passage15 is provided with ports 17 leading into the interior 10A of thecrankcase 10.

Opposite the bracket 18 there is illustrated an induction port for thecrankcase 10. One or more of these ports 18, suitable for handling thevolume of air or airfuel carbureted mixture, may be provided asentrancesinto the crankcase 10. Only one such port is illustrated here, so as tosimplify the drawings, it being understood that the size and/or numberof such ports entering the crankcase is chosen suitably for the volumeof gases requiring inlet into the crankcase. Each induction port (orports) 18 is provided with a check valve to prevent the outflow of gasesfrom the crankcase 10. In the present instance this is illustrated ascomposed of valve leaves 19 attached at 20 to the body of the inductionport 18 and are sized so as to rest against an integral streamlined land21 in the passage through port 18. Gases may flow through the inductionport in the direction of arrow 22, but outflow of these gases isrestrained by the valve leaves 19. Any suitable valve may be used in theinduction port such as the poppet valve, rotary valve, etc.

The crankcase 10 serves to support rotatably a crankshaft 25, which inthe crankcase is provided with one (or two spaced) crank wheels 26,serving to support crank pin 27 on which the lower end of the connectingrod 28 is journalled. In the illustration in FIGURE 1 there is shown asingle crank wheel 26 having an overhanging crank pin 27. Consequently,with such design, the connecting rod 28 need not be split at its lowerend for assembly. A usual connecting rod bearing, not illustrated, is ofcourse, included. The upper end of the connecting rod 28 is journalledby means of a piston pin 29 to the piston 30 which is provided with twoor more piston rings 31. The piston has a dome shaped top, and theheight of the piston is adjusted in relation to the height of the ports14, so that the upper edge of the piston will uncover the full posts 14when the piston 30 is in the lower position, as shown in full lines inFIGURE 1. As the piston travels upwardly it covers the ports 14. Theupper position of the piston 30 is shown in dotted lines in FIG- URE 1.V

The cylinder 11, as previously noted, continues directly upwardly withthe same diameter and at its upper end 11E may be provided with a secondcrankcrase generally designated 32 which is similarly split at theflanges 34 to permit assembly. No crank case closure is actuallyrequired since piston 42 is not required to do any pumping but acrankcase or at least a cover is desirable to keep out dirt and dust andenclose lubricants for the upper moving parts (piston 42, pin 41,connecting rod 38, crankpin 37, crankshaft 35). This crankcase 32provides support for crankshaft 35 having one (or two spaced) crankwheels (cheeks) 36 which support a crankpin 37 on which there isjournalled the crank end of a connecting rod 38. In this illustrationthere is shown one such crank wheel 36 with an overhanging (stub)crankpin 37 and the connecting rod 38 is not split to receive a bearingat the crankpin end. It will be noted that the crankpin 37 is displacedangularly A in advance of the POSI- tion of the related crankpin 27, itbeing noted that rotation is in the direction of arrow 39. The amount ofthis angular displacement may be varied, 10 being typ1cal.

In the upper portion of the cylinder 11 there are a plurality of exhaustports 40. These ports are preferably of equal size and uniformly spacedaround the cylinder 11. The size of these ports 40, is made inaccordance with good design, dependent upon valve timing and gas flowrequirements.

The connecting rod 38 is journalled by means of a pin 41 to a piston 42which is thereby operated up and down in the cylinder 11. Piston 42 isprovided with two or more piston rings 44. The vertical height of thepiston 42 is such that in relation to ports 40, when the piston is inits uppermost position in the cylinder, as shown in FIGURE 1, it willcompletely uncover the exhaust ports 40. It will be noted that thepiston 42, as shown in FIG- URE 1, is beginning its downward travel,hence its lower edge is very slightly below the upper edges of the ports40. In its lower position, shown in dotted lines in FIG- URE 1, ports40* are entirely closed.

A suitable manifold (not shown) is provided around the cylinder 11, andconnected to the exhaust ports 40.

The piston 42 has a slightly dome shaped top and in its lowermostposition is shown in dotted lines. When the pistons 30 and 40 areclosest together, as shown in dotted lines in FIGURE 1, the upper curveddome portion of piston 30 and the corresponding lower curved domeportion of piston 42 are close together but they do not engage eachother. In this position the pistons will have compressed between themthe induced charge and the compression is at maximum at this point. Themovement of both pistons contribute to compression of the charge in thecylinder. The point of maximum compression is shown in FIGURE 1, and theline 44 is halfway between the pistons when they are at such mostproximate, maximum compression position. Around the wall of cylinder 11at line 44-44 there are provided one or more bosses 45-45 in which thereare threaded apertures 4646 to receive spark plugs or fuel injectionnozzles, or both. The bosses are made sufficiently deep so that noportion of the spark plugs (or fuel injection nozzles) will protrudeinto the space between the pistons to cause interference.

In the engines of the present invention the two crankshafts 25 and 35are arranged to be driven together and this may be accomplished bygearing or sprocket and belt or chain drives. For small engines asprocket driven toothed belt operates satisfactorily. In other enginesit may be desirable to provide a gear tower, metal chaintype belt orequivalent drive. In the form shown a toothed belt pulley suitable for aflexible toothed belt is provided at 47 on the crankshaft 28 and anidentical toothed belt pulley of the same size is provided on the crankshaft 35. These are connected together by a toothed flexible belt 49 andconsequently the crankshaft 28 and the crankshaft 35 are driven insynchronism with the position of crankpin 37 leading the position ofcrankpin 27 by the angle A".

The cylinder 11, in the exemplary engine shown in FIGURE 1, has auniform diameter from bottom 11A to top 11B and the pistons 30 and 42are of the same diameter. The displacement accountable to each of thesepistons is accordingly the area of the piston multiplied by the pistonmovement of stroke. Piston movement is, in turn, determined by theradial positions of crankpins 27 and 37 on their respective crank wheels(crank cheeks). The displacement of the lower piston 30 is thus its areatimes the stroke of piston 30 in the cylinder. In this particularengine, which is merely one example of the invention, the stroke ofpiston 30 is made twice as much as the stroke of piston 42, i.e. thecrank radius 27R is made twice as much as crank radius 37R.

According to this invention the piston which accomplishes the exhaustvalving function at the exhaust end of the cylinder may be either onepiston as shown in FIGURE 1, and FIGURE 2, or several pistons as shownin FIGURES 3, 4 and 6. According to this invention the totaldisplacement of this exhaust valve piston (or pistons) accomplishing theexhaust valving function, is made from about to about 50% of the totaldisplacement accountable to the main piston, and is preferably made%-30% of the displacement accountable to such main piston. Thus inFIGURE 1, the movement stroke of the main piston 42 in the cylinderportion 11C may be 50% to 10% of the movement stroke of the exhaustpiston 30 in the cylinder portion 11D, since in this illustration, thetwo pistons are of the same area. The radial dimension 37R determinesthe movement of the piston 42, and this dimension is calculatedaccording to the requirements of exhaust port area and timing.

An increase in the number of exhaust pistons relative to the intakepiston permits a decrease in the total displacement of the exhaustpistons, for any given exhaust port timing and area. Also, a smallerdiameter of the exhaust pistons than of the intake piston produces amore compact and more efficient combustion chamber, and permits a morefavorable spark plug location.

The engine herein described may be either of the type having spark plugsand a carbureted air 'fuel mixture or may be of the diesel type. Inrespect to FIGURE 1, let it be assumed that the induction port (orports) 18 are connected to a suitable carburetor, that spark plugs arepro vided for at the openings 46 and that a suitable exhaust manifold isconnected to ports &0. Under such conditions, and the pistons approachthe positions shown in dotted lines in FIGURE 1, the compression of thepreviously induced charge will occur, due to the combined movement ofthe two pistons 30 and 42. At a suitable time, in advance of reachingthe point of maximum compression, ignition occurs at the spark plugs,and the firing of the thus compressed charge will occur. Both pistonsreach positions shown in dotted lines, and thereafter move away fromeach other, it being noted that rotation is in the direction of arrow39. Since piston 42 leads by some degrees (angle A) the movement of thepiston 30, piston 42 will, at the end of the work stroke uncover thelower edges of the exhaust ports 40 and some outflow of exhaust gaseswill occur at the higher pressure then still maintained in the cylinder,thus initiating an upward flow and outflow through ports 40 of the spentcharge within the cylinder. Also, the height of the ports 40 willgenerally be made such that they will open earlier than the ports 14,even if angle A is zero, or even negative. Meanwhile the downwardmovement of piston'30 is compressing the charge within the crankcase 10,outflow of such charge through the induction port 18 being restrained bythe valves 19. As the upper edge of the piston 30 uncovers theupperedge's of the ports 14, such compressed charge within the crankcase10 will flow through the transfer passages 15 and through the thenopening ports 14. As this flow is desirably distributed generallyuniformly around the cylinder it will move into the cylinder as shown bythe arrows 50. If desired, the lands between the ports 14.1nay besuitably shaped and directed so as to provide any preferred or desiredpattern of flow of induction, the desideratum being that the flow viaarrows 50 should advance frontally and as nearly as possible as a plugof fresh charge which pushes upwardly before it the spent charge whichis then outflowing through the ports 40. Port designs of many kinds areavailable which, cooperation with the shaping of the upper portion ofthe piston uncovering the induction ports, aid in approaching the idealcondition, and such designs may be utilized as desired, they being perse no part of the present invention.

It will be noted that the flow via arrows 50 is a uniflow pattern thespent charge always flowing upwardly and then outwardly through theports 40, as indicated by the arrows 50 and 51.

It has been found that an engine, utilizing the design parameters ofthis invention, illustrated in FIGURE 1 and other embodiments to bedescribed may have an almost perfect fresh charge trapping efficiency upto the scavenging ratio 60%70%, Likewise such engines may be operatedwith high torque at piston speeds of 3000 feet per minute and even up to4000 feet per minute or more, due to the large relative cylinder portarea for induction and exhaust. Such piston speeds are speeds within thelimits of presently available materials, bearings, mechanical balancingetc., as are known in the four-cycle engine art. The specific fuelconsumption of the engines of this invention approximately equal thespecific fuel consumption of four-cycle engines of comparable cylindersize and may be about one-half as much as the specific fuel consumptionof fuel mixture scavenged two-cycle crankcase loopscavenged internalcombustion engines presently available, such engines being the commonlyknown outboard motor engines and similar designs.

Referring now to FIGURE 2, there is illustrated a slightly modified formof engine embodying the invention. In the engine shown in FIGURE 2 thecylinder 11 is made bent, that is to say the upper portion 111D of thecylinder 11 has its axis set at an angle of B to the axis of the lowerportion of the. cylinder which is the cylinder 11. The angle B ispreferably a small angle less than preferably in the neighborhood of 10to 40".

'In FIGURE 2 all portions of the engine below the line 44 are preciselythe same as those already described with reference to FIGURE 1. Thoseportions of the engine which are above the line 44 are similar to thoseshown in FIGURE 1, with the modifications mentioned above. In order tocorrelate the parts of the two engines in FIG- URES 1 and 2, thenumerals designating the parts of the engine above the line 44 in FIGURE2 are the same as those shown in FIGURE 1 except units higher. 7

Thus the upper portion of the cylinder is portion 111D (whichcorresponds to the upper portion 1 1D of FIGURE 1) and has a diameterwhich is less than that shown in FIGURE 1 and its axis is displaced atan angle of B. The amount of this angular displacement may be varied. Itis less than 90 and is prefer-ably about 10 to about 40. illustrated ischosen to permit a compact combustion chamber with desirable location ofa spark plug boss and aperture at 61-62. Also this provides a squisharea which produces a desirable degree .of turbulence as the charge iscompressed. The reduction of diameter of the portion 111D of thecylinder ascompared to portion '1'1C permits the use of a somewhatlonger stroke 137R, as compared to crankstroke 37R of FIGURE 1, and alsomakes for a more compact combustion chamber. In the engine shown inFIGURE 2 the volumetric displacement attributable to the piston 142moving in the cylinder 111D is the same as'in the engine shown in FIGURE1, namely about 10% to about 50%, preferably about 20% to about 30% ofthe displacement attributable to the movement of piston 30 in theportion 11G of cylinder 11. Since the diameter of the cylinder 11 isdecreased, above line 44 44, the crank throw of crank 137 may beincreased somewhat. Ports 14.4 and their positions are proportionedaccording to the dictates of area and timing and fully open when thepiston is in its uppermost position, as shown in full lines in FIGURE 2.Otherwise the upper portion of the engine shown in FIGURE 2 is the sameas that shown in FIGURE 1, the crank case 132 being split at the flangesThe amount of angular displacement specifically 134 so as to permitassembly of the crankshaft 135, having 'crankwheel 136 and crankpin 137thereon. The piston 142 is connected by the connecting rod 138 to thecrankpin 137. Again, the crankshaft 137 is provided with a toothedsprocket 148 which is connected by the toothed belt 149 to the toothedsprocket 47 on the lower crankshaft 25.

The pistons 30 and 142 may be relieved with reference to each other sothat they do not engage when they are in the dotted line position. Thusdepartures may be made from the simple dome design, so as to improvecombustion chamber layout. It will be appreciated that if the angle B isdesired to be decreased, that this can be done by reducing the size ofthe spark plug boss 61.

The rotation of the upper crankshaft 135 is as shown by arrow 139 andthe crank pin 137 leads by A the rotation of the crankpin 27. As thepistons 30 and 142 approach their dotted line positions, as shown inFIGURE 2, they compress between them the previously induced charge, andshortly prior to reaching a point of maximum compression the spark atspark plug 64 ignites the charge and the power stroke begins, thepistons being driven away from each other during the power stroke. Theupper edge of the piston 142 reaches the lower or leading edge of theexhaust ports 144 in advance of the time that the upper edge of thepiston 30 reaches the upper edge of the induction ports 14 andconsequently the expanding charge, which is still under a considerablepressure within the cylinder, is permitted to escape through the ports144, in the direction of arrows 151.

The downward motion of the piston 30, as previously described,compresses the previously induced charge in the crankcase 10, and as thepiston 30 begins to uncover the upper edges of the ports 14, this chargecompressed within the crank case will pass upwardly through the transferpassageway and through the ports 14 and into the cylinder 11. Thischarge flows upwardly via arrows 50, the desideratum, as previouslymentioned, being that it shall advance frontally pushing upwardly beforeit the already burned and spent gases which are moved more or less as aplug upwardly, and consequently in an upward unifiow direction, withresult that they are caused to flow out through the exhaust ports 144via arrows 151. While the ideal condition of no mixing between theinflowing and outfiowing charges is most diflicult of attainment, yet ithas been found that in the present engine a minimum of such mixing canbe attained with the consequence that there is experienced a specificfuel consumption in this two-cycle uniflow crankcase-scavenged engine,which is comparable to the specific fuel consumption in the best qualityof four-cycle engines of similar cylinder size, and the horepower outputof the engine of the present invention will, on an equivalent basis,approach approximately twice as much as that of an overhead-valvefourcycle engine.

In FIGURES 1 and 2, in each of the engines illustrated the cylinder 11has a lower cylinder portion 11C and one upper cylinder portion (11D or111D) and one piston in the latter portion serves to perform the exhaustvalve function for the whole two-portion cylinder 11. Thus in FIGURE 1it is a simply the upper portion 11D of the cylinder 11, together withthe piston 42, which serves to perform the exhaust valving function. InFIGURE 2 the upper portion 111D of the cylinder 11 is made of somewhatsmaller diameter than the lower portion 11C of cylinder 11 and is set atan angle B with reference to the axis of the cylinder 11. According tothe present invention the exhaust valve cylinder portion may be made asone or two or more cylinders. Thus in FIGURE 3 there are two upperportions of cylinder 11, these being the two cylinder portions 111R and111L. These two cylinder portions 111R and 111L perform theexhaust'valving function for the whole cylinder of which the mainportion is 110. In FIGURE 6, four such cylinders (upper cylinder)portions are provided, these being the cylinder portions 211A, 211B,211C 8 and 211D, see FIGURE 7, and these in concert perform the exhaustvalving function.

According to the present invention the total Volume of the cylinderportion (or portions) which perform the exhaust valving function may beone such cylinder portion as in FIGURES l and 2, or may be two suchcylinder portions as shown in FIGURE 3 or more than two cylinderportions as shown in FIGURES 6 and 7. An advantage of using a greaternumber (than one) of such cylinder portions for performing the exhaustvalving functions is that a greater wall area and hence greater exhaustport area is thus provided around the periphery of several cylinderportions, for a given displacement volume devoted to such upper cylinderportions. It is to be understood that regardless of the number ofexhaust cylinder portions used for each main (or wor or induction)cylinder portion, the total of their volumes (whether one, two, four ormore) is from about 10% to about 50% of the volume of the main clyinderportion, preferably about 20% to about 30% thereof. However, the greaterthe number of exhaust pistons per main piston, the smaller the relativeexhaust piston displacement is generally required in order to achieve agiven exhaust port area and timing. Also, with a greater number ofexhaust pistons more freedom results in spark plug location andcombustion chamber shaping, leading in turn to increased thermalefficiency.

In FIGURE 3 those parts of the complete engine which are below the line4444 (which is also section line 55, in this illustration) are the sameas in FIGURES 1 and 2 and therefore need not be described again.Comparing FIGURES 2 and 3, while FIGURE 2 had one exhaust valvingcylinder portion 111D, the engine shown in FIGURE 3 has two exhaustvalving cylinder portions 111R and 111L. The numbers applied to thevarious parts of these two cylinder portions correspond to those shownin FIGURE 2 except that they are designated R and L depending on whetherthey are the right (exhaust) cylinder portion or the left (exhaust)cylinder portion. Thus the right cylinder portion 111R is provided witha piston 142R operated by the piston pin 141R and connecting rod 138R,crankpin 137R on crankshaft R operating in the crankcase 132R. Preciselythe same parts are shown for the cylinder portion 111, these beingdesignated with the L sufiix and corresponding numerals. Both the crankshafts 135R and 135L are provided with drive pulleys 148R and 148L whichare driven through a toothed belt 149RL from the driving pulley 47 onthe crankshaft 25. Accordingly all three crankshafts (25, 135R and 135L)and their related parts, are moved in synchronism in the direction ofarrows 139R and 139L. The crankpins 137R and 137L may lead by a fewdegrees (Angle A) the motions of the crankpin 27, as previouslydescribed with reference to FIGURES 1 and 2. When the piston 30 andpistons 142R and 142L are adjacent, they are in the position shown indotted lines FIGURE 3. It may be noted that the pistons 142R and 142Lmay be provided with upper surfaces which are dished, so as together toprovide a compression space 70 which is more or less dome-shaped, andapproaches the theoretical ideal in design. Two apertures for sparkplugs are provided at 64, and the plugs 64A and 64B (see FIGURE 4) maybe provided in the dome. A desirable central location for the sparkplug(s) is thus provided. For the purpose of mechanical simplicity, onlya single spark plug may be utilized. One or more of the spark plugs maybe replaced by fuel injection nozzles, as desired.

In operation the piston 30 and the pistons 142R and 142L in concertapproach each other, moving from their full line positions to theirdotted line positions as shown in FIGURE 3, thereby compressing thepreviously induced charge between them. Just prior to reaching the pointof maximum compression the spark occurs or in the case of a dieselengine fuel is injected. Thus the ignited charge drives against thepistons, which then begin to move away from each other in sychronismaccording to the motions of the crankshafts 2.5 and 135R and 1351., andtheir related parts. The timing of the motions of the pistons 142R and142L is such that they begin to uncover the lower edges (leading edges)of the exhaust ports 144R of cylinder 111R respectively of the exhaustports 144L of cylinder 111L, slightly in advance of the time that thepiston 30reaches the upper edges of the ports 14. Consequently theburned gases, which have of course expanded due to the motion of thepistons but which are still at a considerable pressure within thecylinder, are permitted to pass out through the ports 144R and 144L, andthrough the exhaust manifolds, not shown. Shortly thereafter, as thepiston 30 begins to uncover the upper or leading edges of the ports 14and the charge (which as described with reference to FIGURES 1 and 2 hasbeen compressed in crankcase is permitted to pass through the transferpassageway and through the ports 14, moves as shown by the arrows 50into cylinder 11, where in a unifiow form of motion such gases-move withminimum intermixing with the exhaust gases above them and push suchgases upwardly into the two exhaust cylinder portions 111R and 111L andvia arrows 151R and 151L out through the exhaust ports 144R and 144L.

The greater number of exhaust cylinder portions 111R and 1111, (twoinstead of one) for controlling the exhausting of the gases, provides agreater total dimension of cylinder wall periphery per unit volume(equalling the peripheries of the cylinder portions 111R and 111L addedtogether) wherein the designer may place exhaustports 144Rand 1441.. Amore favorable combustion chamber shape and spark plug location, ascompared with use of a single exhaust piston as in FIGURES 1 and 2, alsoresults.

Where complexity is not objectionable, an even greater number of exhaust(supplemental) cylinder portions may be utilized, this being illustratedin FIGURES 6 and 7 where a total of four such cylinder portions 211A,211B, 211C and 211D are provided. Whereas FIGURE 3 shows a simple Vofupper exhaust cylinder portions, these being 111R and 111L in theengines shown in FIG- URES 6 and 7, there are in FIGURE 6, two blankshaving two exhaustcylinder portions, making a total of four cylinderportions for providing the exhaust func tion. Even more might beprovided if the matter of complexity is not objectionable. In the engineshown in FIGURES 6 and 7, the one bank of such exhaust cylinder portionsare the cylinder portions 211A and 211B (see FIGURE 7 and FIGURE 6) andthe other bank of cylinder portions are 211C and 211D. These are madeprecisely similar to those shown in FIGURE 3 and need not be furtherdescribed. Each cylinder portion has a piston, each piston is made asshown in FIGURE 3 so as to uncover cooperating exhaust ports. Thepistons in cylinder portion 211A and 211B are operated by a singlecrankshaft 235L which operates in the crankcase232AB. On this crankshaftis a pulley 248L which is driven by the belt 249RL. A similar crankcaseand crankshaft and pulley (not shown, as these would be behind 232AB,235L and 248L) are provided for operating in unison the pistons in thecylinder portions 211C and 211D.

Taken together the volumetric displacement accountable by the pistonsmoving in supplemental (exhaust) portions 211A through 211D shall beabout 10% to about 50% preferably about to about of the volumeaccountable by the movement of piston 30 within the main cylinderportion 110. The arrangement shown in FIGURES 6 and 7 has the additionaladvantage of providing a dome-shaped compression chamber together with acentral location of a single spark plug or fuel injection nozzle at 64X.Otherwise the engine is the same as illustrated and previously describedwith reference to the other figures.

Throughout this specification and in the claims the term cylinder isintended to include the entire communicating space served by all pistonsin it, including the configuration of FIGURE 1 wherein the cylinder isof one uniform diameter and is served by two pistons; the configurationof FIGURE 2 where cylinder portions of different diameters are used andthe configurations of FIGURES 3-7 where a main cylinder portion is indirect communication with but is branched into two or more supplemental(exhaust) cylinder portions.

The engines shown in FIGURES 1, 2, 3 and 6, in each instance illustratea one cylinder engine. It will be understood that all of theseillustrated engines can be made multiple cylinder engines by merelyadding more cylinders in parallel or in angular configuration, as iswell known, with appropriate lengthening of the crankcases andcrankshafts. Usually only one drive arrangement will suffice for drivingthe crankshafts in unison, regardless of the number of cylinders servedby the crankshafts.

It'will also be noticed that in each of the engines described andillustrated, the displacement volume of the crankcase pumping means-issolely associated with the crank shaft of the induction piston. Theexhaust pistons and crankshafts have no function as crankcase scavengingpumps; By this means any difficult and troublesome transfer piping fromthe exhaust. piston crankcases to the cylinder induction ports iseliminated and at the same time the full throttle delivery ,orscavenging ratio can be kept to'a desirable percentage in the interestof low spe cific fuel consumption. It should also be pointed out thatthe motion of the exhaust pistons is in general diametrically opposed tothat of theinduction piston, permitting an engine of nearly perfectreciprocating force balance.

As many widely apparently different embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that I do not limit myself to the specific embodimentsherein.

What I claim is:

1. An improved two-cycle crankcase-scavenged internal combustion enginecompirsing:

a cylinder having a main cylinder portion and a supplemental cylinderportion directly connected to each other,

a main piston in said main cylinder portion, and a supplemental pistonin said supplemental cylinder portion,

a main crankcase for said main cylinder portion having a main crankshafttherein,

a main connecting rod connecting the main crankshaft and main piston foroscillating the piston as its crankshaft rotates,

an induction passage into the main crankcase having value means thereinfor preventing outflow of gases from the main crankcase when gases arecompressed therein,

induction ports in the wall of the main cylinder portion positioned tobe uncovered by the main piston as it is moved towards the maincrankcase by the main connecting rod and main crankshaft, transferpassages connecting said induction ports to the interior of the maincrankcase;

said main crankcase and main piston forming the sole pumping means forscavenging said cylinder,

a supplemental crankcase for said supplemental cylinder portion, havinga supplemental crankshaft therein,

a supplemental connecting rod connecting the crankshaft and supplementalpiston for oscillating said supplemental piston as its crankshaftrotates,

exhaust ports in the wall of the supplemental cylinder portionpositioned to be uncovered by said supplemental piston as it movestowards said supplemental crankcase,

mechanical means connecting the main and supplemental crankshafts fordriving them in unison and for thereby reciprocating the main andsupplemental pistons towards each other and then away from each other,

the dimensions of the portions of said cylinder and the amount ofmovement of the pistons therein being such that the volume displaced bythe movement of the supplemental piston is from about to about 50% ofthe volume displaced by movement of the main piston, an opening forignition means fuel injecting means or the like in the cylinder andleading into that portion of said cylinder which is between the pistonswhen they are closest together.

'2. The engine of claim 1 further characterized in that the volumedisplaced by the movement. of the supplemental piston is in the range ofabout 20% to about 30% of the volume displaced by the movement of themain piston.

3. The engine of claim 1 further characterized in that the axis of thecylinder portions are at an angle to each other.

4. The engine of claim 1 further characterized in that the supplementalcylinder portion is of the same diameter as the main cylinder portion.

5. The engine of claim 1 further characterized in that the supplementalcylinder portion is of a lesser diameter than the main cylinder portion.

6. The engine of claim 1 further characterized in that the supplementalcylinder portion is of a lesser diameter than the main cylinder portionand further characterized in that the axis of the cylinder portions areat an angle to each other. 7

7. The engine of claim 1 further characterized in that there are twosupplemental cylinder portions in communication with the main cylinderportion, each having its supplemental crankcase, crankshaft connectingrod and piston, each of said supplemental crankshafts being connected tosaid main crankshaft by said mechanical means so as to turn in unisontherewith.

8. The engine of claim 1 further characterized in that there are twosupplemental cylinder portions in communication with the main cylinderportion, each having its supplemental crankcase, crankshaft connectingrod and piston, each of said supplemental crankshafts being connected tosaid main crankshaft by said mechanical means so as to turn in unisontherewith and said supple mental cylinder portions having axes that areat an angle to the axis of the main cylinder portion.

9. The engine of claim 1 further characterized in that there are twopairs of supplemental cylinder portions in communication with said maincylinder portion.

10. The engine of claim 9 further characterized in that the axes of thesupplemental cylinder portions of each pair are in a common locationplane and the location planes of the axes for both pairs are at an angleto the axis of the main cylinder portion.

11. The engine of claim 1 further characterized in that there are twopairs of supplemental cylinder portions in communication with said maincylinder portion, each pair of said supplemental cylinder portionshaving a common crankshaft, said two crankshafts one for each pair ofsupplemental cylinder portions being driven in unison from said maincrankshaft by said mechanical means.

References Cited by the Examiner UNITED STATES PATENTS 871,539 11/07 VanAuken 123-51 1,273,229 7/ 18 Hurlbrink 123-51 1,699,111 1/29 Lyons123-51 2,054,232 9/36 Schneider 123-51 2,367,565 1/45 Curtis 123-652,639,699 5/53 Kiekhaefer 123-73 2,669,979 2/54 Kiekhaefer 123-732,768,616 10/56 Venediger 123-51 2,831,359 4/58 Carle 123-90.102,886,018 5 5 9 Cuddon-Fletcher 123-51 2,894,405 7/59 Carle 123-4952,949,899 8/60 Jacklin 123-51 FOREIGN PATENTS 20,063 9/09 Great Britain.225,249 1 l 24 Great Britain.

FRED E. ENGELTHALER, Primary Examiner.

1. AN IMPROVED TWO-CYCLE CRANKCASE-SCAVENGED INTERNAL COMBUSTION ENGINECOMPRISING: A CYLINDER HAVING A MAIN CYLINDER PORTION AND A SUPPLEMENTALCYLINDER PORTION DIRECTLY CONNECTED TO EACH OTHER, A MAIN PISTON IN SAIDMAIN CYLINDER PORTION, AND A SUPPLEMENTAL PISTON IN SAID SUPPLEMENTALCYLINDER PORTION, A MAIN CRANKCASE FOR SAID MAIN CYLINDER PORTION HAVINGA MAIN CRANKSHAFT THEREIN, A MAIN CONNECTING ROD CONNECTING THE MAINCRANKSHAFT AND MAIN PISTON FOR OSCILLATING THE PISTON AS ITS CRANKSHAFTROTATES, AN INDUCTION PASSAGE INTO THE MAIN CRANKCASE HAVING VALUE MEANSTHEREIN FOR PREVENTING OUTFLOW OF GASES FROM THE MAIN CRANKCASE WHENGASES ARE COMPRESSED THEREIN, INDUCTION PORTS IN THE WALL OF THE MAINCYLINDER PORTION POSITIONED TO BE UNCOVERED BY THE MAIN PISTON AS IT ISMOVED TOWARDS THE MAIN CRANKCASE BY THE MAIN CONNECTING ROD AND MAINCRANKSHAFT, TRANSFER PASSAGES CONNECTING SAID INDUCTION PORTS TO THEINTERIOR OF THE MAIN CRANKCASE; SAID MAIN CRANKCASE AND MAIN PISTONFORMING THE SOLE PUMPING MEANS FOR SCAVENGING SAID CYLINDER, ASUPPLEMENTAL CRANKCASE FOR SAID SUPPLEMENTAL CYLINDER PORTION, HAVING ASUPPLEMENTAL CRANKSHAFT THEREIN,